Related Products

AP Racing

CP8350

Hard Anodized Finish

The first obvious weakness when looking
at a typical aftermarket caliper is the finish. Most aftermarket
calipers come in a painted finish, whether they are red, black, or gold.
That painted finish is designed to look pretty and prevent corrosion in
harsh winter environment. Unfortunately, for all of the compliments
painted calipers generate, there is an associated price if you drive the
car in a track environment. That price is the chipping, flaking,
fading, color shift, and general degradation of that finish in a fairly
short period of time. Some OEM calipers can go from the as-delivered
color to a nasty shade of brown in as little as one weekend. While this
is typically worn as a badge of honor among our more hardcore customers,
let’s face it…they still look terrible. More importantly however, all
of those bits of paint end up in places they’re not supposed to, which
we’ll get to in a minute.

Why does this happen? Heat. Paint and powder coat cannot
adequately handle track temperatures. Powder coat also has some
notorious issues with shrinkage. The powder coat layer expands and grows
when the caliper is heated. When it cools, the powder coat doesn’t
necessarily shrink in step with the caliper body itself. What’s left is a
loose shell of finish hanging limply on the caliper body. That shell
then cracks and falls to pieces.

Paint can also have similar issues depending on how it is
applied. If you were to line up a few aftermarket calipers from the same
manufacturer, you would likely see that the painted finish on each of
those calipers is slightly different. Some have a thicker coat, some
thinner, slightly different shades of red, etc. Painting is to some
extent an art form, and must be performed in a tightly controlled
environment. If it isn’t, you’re always going to see variation. A thick
coat makes the part look soft around the edges, and is prone to cracking
off in the same manner as the powder coat described above, leaving the
underlying finish exposed. A part without enough paint will look uneven,
and will not protect the underlying aluminum particularly well either.
In addition to problems with cracking, flaking, and uneven application,
paint and powder coat also experience extreme color shift when heated.
Red becomes maroon or black, gold becomes brown, and black just gets
uglier.

The calipers we are using in the Essex Competition Kits
are ultra-lightweight, stiff, and durable under all track conditions.
The finish is a hard anodizing, which is the business under track
conditions. When raw aluminum reacts with the oxygen in the air, a hard
surface film develops on aluminum which prevents further degradation.
The process is called oxidation, and you can think of it like rust. The
anodizing process leverages this natural phenomenon, and takes it a step
further to produce an extremely hard protective layer of aluminum oxide. It does so by running an electrical current through an
acid bath, and dying it to the desired color. If you want to know more,
Google it.

The result is a finish that is far more appropriate for racetrack
use. Anodizing creates a uniform surface that is much more abrasion
resistant than paint or powder coat. That means if you ding an anodized
caliper with a box wrench when bleeding it, a big chunk of the finish
isn’t going to chip off into your hand. While anodized calipers will
still exhibit color shift, it will take a lot more heat to get them to
change, and they won’t change as dramatically. More importantly though,
you aren’t going to have bits of anodizing sticking to the sides of your
pistons.

20mm Thick Brake Pads in A Commonly Available Shape

Race
pads aren’t cheap, and you burn through them quickly if you spend any
amount of time on track. The average set of race pads for the AP Racing
CP8350 costs roughly $175. How many sets of brake pads do you go
through in a
season? Some people find that they could pay off their brake system in a
short period of time on pad savings alone. Not only are the pads for
the CP8350 inexpensive, they’re also 20mm thick. That extra thickness
acts as a thermal
barrier and helps keep heat out of your pistons and brake fluid.
Finally, since this pad shape is used by a wide range of racing
calipers,
it’s available in just about every popular racing compound on the market
(Essex
alone sells close to 20!). That means you’ll never end up in a pinch
without pads. Cheap, thick, and available is a great combination for a
consumable like race pads.

Below is a drawing of the basic pad shape used in the CP8350:

Dimensions= 133.2mm x 60.0mm x 20.0mm

The available pad compounds that Essex sells for the CP8350
caliper can be found below. Please keep in mind that there are many
other compounds available on the market from other manufacturers. The
list below represents only what Essex sells. When purchasing our
system, you have the option of buying one set of brake pads for $25.
Underneath the manufacturer list below, the pad
compounds are listed from most aggressive to least aggressive.

CL Brakes

RC8

RC6

Ferodo Racing

DSUNO

DS3000

DS1.11

DS2500

Hawk Performance

DTC-05

DTC-70

DTC-60

DTC-30

HT-10

HP+

Black

MT-4

HPS

Note on using brake pads different from those listed above

Again,
please keep in mind that the above is not an exhaustive list, and that
there are many other pad compounds available in this shape from other
manufacturers.
Please note however, that the pad
shape we use
in our caliper is available in a variety of radial depths (heights).
When combined with the CP3908 325x32mm disc, Essex recommends the 50mm
radial depth version.
Other
common radial depths in this pad shape are 43mm and 39mm. Those radial depths will
fit into our caliper, but you will be leaving an unswept 'ring' around
the disc near the attachment points to the hat (the pad will not hang as
low in the caliper). Leaving a portion of the disc face unswept can
create a temperature differential across the face of the disc, and doing
so
could lead to premature disc cracking. That said, we have not run into such a problem with our kits in the field.

Pad Cross Reference Since
we do not sell most of the brands listed below, Essex cannot guarantee
the fitment of these pads in the AP Racing CP8350 caliper. Based on our research
however, we believe that these are the appropriate cross references for
the basic shape. However, you should verify with either the
manufacturer or your installer prior
to purchasing any of them.

D43 Depth

D50 Depth

Manufacturer

Part Number

Part Number

Carbotech

CTW7420

CTFRP3116

Circo

MB1680

MB2660

Endless

RCP106

RCP106

Ferodo

FRP3097

FRP3116

Hawk

HB521.800

NA

Pagid

2205USA

NA

PFC

7751.xx.20

NA

Project Mu

999

NA

Raybestos

R701

NA

Wilwood

7420

NA

Stainless Steel Pistons

There are people who will tell you that aluminum pistons
are great for track calipers. They will tell you that the expansion
rates of the pistons and caliper body need to be the same when heated.
This argument is completely invalid and unproven. Those same people
tend to get upset when you point out the fact that every serious race
caliper, from every serious race caliper manufacturer on the planet uses
either stainless steel or titanium pistons, period. There is a reason for
this: they're better!

While most aftermarket calipers use a
pressed aluminum piston, the CP8350 uses an expensive machined
stainless steel piston. Aluminum has a much higher thermal conductivity
than stainless steel, and therefore transmits heat into your brake
fluid much more quickly. That is exactly what you don't want!
Stainless steel pistons are far superior
to aluminum pistons in creating a thermal barrier. They help keep heat
out of your brake fluid, preventing a soft pedal (brake fluid fade) on
the track. This has been proven over and over again
at all levels of motorsport.

Titanium pistons are a great option, but they are hideously

expensive. Stainless steel offers the greatest balance of heat

reduction, weight, and price. They also alleviate the need for crutch

solutions such as fitting a titanium shim between the brake pad and

highly conductive aluminum pistons

Anti-knockback Springs

Not only are the domed back pistons ventilated stainless steel, they
are also fitted with anti-knockback springs. Springs behind the pistons you ask?
Yes, springs. If you’ve ever gone through a series of S turns and then
had your pedal drop when going into the following brake zone, you have
experienced knockback. To say it is disconcerting is an
understatement. You’ll often see pro drivers ‘pre-tap’ their brakes
lightly when approaching a brake zone. They are fighting knockback.

Knockback
is a phenomenon that is common with fixed calipers. Knockback occurs
when your car’s wheel, hub, and bearings deflect during cornering,
allowing your brake disc to move out of sync with your caliper and brake
pads. The caliper is less prone to movement because it is attached to
the more rigid upright. As the brake disc deflects, it actually pushes
the pads away from each other, forcing the caliper pistons back into
their bores. The piston seals don’t have enough tension in them to
return the pistons to their original location. That means there is
slack in the system that needs to be taken up. When you press the brake
pedal, it will continue to drop until that slack is taken up.

Anti-knockback springs help alleviate this situation by putting
some tension on the back side of the pistons. When the disc deflects
and makes contact with the pistons, the springs push the pistons back
into their proper location, reducing slack in the system. That means
less pedal drop and far fewer pucker-factor moments when going into
heavy brake zones.

There are no major downsides to lightweight AKB spring as long as
the caliper is designed to accommodate them. More specifically, AKB
springs do not create any increased drag or wear on the pads and discs
as long as the shape and material of the piston seals takes them into
account.

As you're driving the suspension is constantly compressing, the
disc is moving around laterally, and the pads are being pushed slightly
away from the disc. Think of the seals in the caliper as a spring or
hinge attached to the side of the piston, rather than just a ring
through which the piston slides. In an AP Racing competition caliper,
the groove in which the seal resides isn't a square cut groove.It has
angles. When the pistons slide in or out there is friction between the
outer piston wall and the seal, and the seal distorts a bit as shown in
the illustration below.

A caliper piston sliding out to the left would distort the seal in

this manner (the slashes are the seals on either side of the piston):

/ --- --- \

As the piston slides back in to the right, the seal does this: \ --- --- /

There is a certain amount of tension or friction that needs to be
overcome before the piston actually starts moving through the seal ring.
That tension/friction keeps the piston from dragging on the disc once
the pistons are pushed back into the bores by the disc/suspension
movement.

When AKB springs are added, a little more force is
required to push the pistons back into their bores than would be
required without them. After the spring is compressed, it unloads and
pushes the piston back to 'neutral.'

With the proper seal and
spring the goal is to keep the piston in the 'neutral' position, not
pressed against the disc. The piston is still able to slide freely in
either direction, but a bit of friction or tension needs to be overcome
initially to get it moving in either direction. The seal offers that
first bit of friction to limit movement, and then the spring provides
additional resistance. The end result is that the properly designed AP
Racing calipers won't drag or create additional or unnecessary wear,
despite having springs behind the pistons.

High Temperature, Low Drag Seals Without Dust Boots

We are often asked by potential customers if the calipers in our kits
require frequent maintenance and rebuilding because the pistons don't have
dust boots. We are perpetually shocked by this question because it makes
no intuitive sense. If you have a product that is specifically designed
to handle the extraordinary high-heat conditions of track use, why would it
require more maintenance when used under those conditions vs. brake components
that were designed to cruise around on the streets at low speed and temperature?

Many people confuse piston seals with dust boots. All calipers have seals.
They're the little rubbery rings inside the piston bores (see pic below). If a
caliper didn't have a seal, your brake fluid would leak out around the pistons!
OEM caliper seals aren’t designed to handle constant trips to several
hundred degrees without becoming brittle and leaking. Our calipers use special
high-temp seals designed for track use. They are the exact same high
temperature seals used in NASCAR Sprint Cup, ALMS, DTM, etc. That means they
are less likely to get brittle and wear out when used under high-heat track conditions,
and they require far LESS frequent replacement and servicing.

Most aftermarket calipers are designed for year round road use,
and as such
come with a bellows style external dust boot like the ones shown below.
The rubber boot stretches as the piston extends, and its objective is
to keep contaminants out of the piston bore. It's a nice concept, but
we've seen customers burn those up
in a single 20 minute track session!
Once that happens, you're simply driving around with some tattered,
burnt
rubber bits attached to your pistons. At that point they're providing
zero benefits to
you. If you're going to instantly destroy them when you go to the
track, why worry about having them in the first place? We skip making
that mess for you by eliminating them from our design.

AP Racing High-Temp Piston Seal

OEM Dust Boot Before Track Use

OEM Dust Boot After Track Use

Simple Pad Change with One Bolt

After the countless times you’ve changed your brake pads, you’re
probably never too excited when it comes time to do so. Changing pads
will no longer be a chore. No more fiddling with a
hammer, punch, or pliers. AP’s bridge bolts pop out easily with a 5mm
hex wrench and a 7mm socket. It will take you longer to pull off the
wheel than it will to change pads. Less time futzing around in the
paddock, and more time driving= fun.

Pistons Sized Specifically for Your Car

The
piston sizes in our systems are specifically chosen to closely mimic
the OEM brake torque on a given axle. As such, our front systems can be
bolted to otherwise stock cars with no ill-effects, negative impact on
ABS, etc. The vehicles
stock master cylinder can remain, as can the OEM rear brake system.

Integrated Bleed Screw and Crossover Tube Protection

How often do you take the wheels on and off of your track
car? At least once per event? A 30lb. wheel and tire combo can do
quite a bit of damage when it collides with a caliper's bleed screw or
crossover tube. Of the hydraulic components shown below, which do
you think have better impact protection?

The CP8350's body was designed to protect the bleed screws and crossover
piping from heavy-handed crew members and track debris. These delicate
hydraulic components reside in small coves on the caliper body that can
withstand the impact of a wheel, tool, rock, etc. Wheel, pad, and
fluid changes become less worrisome and faster, and less time in the
pits equals more time on the track.

Ultra-lightweight, Compact Design

The Essex mantra when designing brake kits has always been, "Anything larger than
necessary to get the job done is simply dead weight to drag around," and the CP8350 aligns perfectly with those values. One
of the major problems with many of the brake packages currently on the
market is wheel fitment. You’re offered gigantic discs and 12 piston
calipers, with a pat on the back and a, “Good luck finding wheels to
clear those things (insert sinister chuckle here).” The reality is that
many casual racers want to use their OEM wheels on the track, or
the smallest, lightest wheel they can find. Not only is saving unsprung
weight critical, R compound tires are much more plentiful and cheaper
for smaller wheels. If the components are designed properly with heavy
use in mind, you don’t need to cram boat anchors under your wheels. If you’re
worried about the loss of stiffness due to mass reduction, don’t. Some
manufacturers use a heavier six piston caliper, but that's because the
caliper wasn't designed or optimized for racing. In those cases, the
same caliper may have been designed for use on much heavier road cars,
and even trucks! AP Racing’s CP8350 calipers are incredibly stiff, and designed from
scratch with only the racetrack in mind.

Lifetime Professional Reconditioning Service

Essex
is AP Racing's official North American caliper reconditioning center.
We have skilled service technicians rebuilding hundreds of AP Racing
calipers each year for the top teams in NASCAR Sprint Cup, ALMS, etc.
As an Essex customer, our rebuild service will always be available to
you when your calipers need servicing. You simply remove your calipers
from the car, drain/clean them, and ship them back to Essex. We take it
from there:

Hardness testing:
After disassembly your calipers will be Rockwell hardness tested
against the standard for that particular caliper type as sold new. This
test provides a relative understanding of how much fatigue and stiffness
loss your calipers have experienced. Tired calipers lead to pad
tapering, increased pad wear, leaky seals, and a loss of pedal firmness,
all things you want to avoid. Essex will make a replace or rebuild
recommendation based on the results of this test.

Ultrasonic cleaning:
After passing the hardness test, your calipers will be placed in an
ultrasonic cleaner to remove all dirt, debris, brake fluid, etc. This
method produces results that are far superior to what the average racer
could accomplish via hand-cleaning.

Inspection and re-assembly:
All serviceable parts of the caliper will be inspected and replaced if
necessary, including the seals, abutment plates, pistons, and bleed
screws.

Cyclical Pressure Testing:
After your calipers have been rebuilt, they will be cycled at high and
low pressure on a pressure bench to ensure proper functioning. This is
important, as certain leaks only show up under specific pressure
conditions.

Price:
The labor price to rebuild is roughly $80 per caliper. That does not
include parts. Assuming there has been no damage to the caliper, Essex
typically recommends replacing the seals ($60) and bleed screws ($15)
during the standard reconditioning process. For roughly $160, you can
have a fresh, professionally serviced caliper in peak operating
condition. You won't get messy, and you'll know the rebuild was done by
the same folks trusted by elite-level race teams.

Caliper

CP8350-24S4L/25S4L

Weight no Pads

4.8lbs.

Piston Sizes

38.1mm x 2

41.3mm x 2

Piston Area

49.56cm^2

Inlet Thread

M10x1.0

Mounting Type

Radial

Mtg. Centers

152mm

Mtg. Offset

44mm

Pad thickness

20mm

Disc Diameter - mm

- Max = 330.0 - Min = 280.0

Disc Thickness - mm

- Max = 32.0 - Min = 32.0

Brake Pads

The Brake Pads compatible with the AP Racing CP8350 caliper:

The available pad compounds that Essex sells for the CP8350 caliper
can be found below. Please keep in mind that there are many
other compounds available on the market from other manufacturers. The
list below represents only what Essex sells. When purchasing our
system, you have the option of buying one set of brake pads for $25.
Underneath the manufacturer list below, the pad
compounds are listed from most aggressive to least aggressive.

CL Brakes

RC8

RC6

Ferodo Racing

DSUNO

DS3000

DS1.11

DS2500

Hawk Performance

DTC-05

DTC-70

DTC-60

DTC-30

HT-10

HP+

Black

MT-4

HPS

Note on using brake pads different from those listed above

Again,
please keep in mind that the above is not an exhaustive list, and that
there are many other pad compounds available in this shape from other
manufacturers.
Please note however, that the pad
shape we use
in our caliper is available in a variety of radial depths (heights).
When combined with the CP3908 325x32mm disc, Essex recommends the 50mm
radial depth version. Other
common radial depths in this pad shape are 43mm and 39mm. Those radial depths will
fit into our caliper, but you will be leaving an unswept 'ring' around
the disc near the attachment points to the hat (the pad will not hang as
low in the caliper). Leaving a portion of the disc face unswept can
create a temperature differential across the face of the disc, and doing
so
could lead to premature disc cracking. That said, we have not run into such a problem with our kits in the field.

Pad Cross Reference Since
we do not sell most of the brands listed below, Essex cannot guarantee
the fitment of these pads in the AP Racing CP8350 caliper. Based on our research
however, we believe that these are the appropriate cross references for
the basic shape. However, you should verify with either the
manufacturer or your installer prior
to purchasing any of them.